The amount of calcium present in milk can be determined through gravimetric analysis by adding oxalate to a sample and measuring the mass of calcium oxalate precipitated. What is the mass percent of calcium in milk if 0.429 g of calcium oxalate, CaC2O4, forms in a 125-g sample of milk when excess aqueous sodium oxalate is added?

Na2C2O4 (aq) + Ca2+ (aq) → CaC2O4 (s) + 2 Na+ (aq)

0.343%
1.10%
1.37%
0.202%
0.107%